published_or_final_version / Psychiatry / Master / Master of Philosophy

No description available.

No description available.

No description available.

No description available.

No description available.

Definition of neurodevelopmental outcome from early brain imaging remains a priority for survivors of very preterm (VPT) birth given their persistently high rates of cognitive and motor difficulties. Volumes of the deep grey matter (DGM) structures were measured longitudinally using magnetic resonance imaging from 96 VPT infants studied within 2 weeks of birth and 70 at term-equivalent age. At 4 years of age, 36 children returned for neuropsychological assessments evaluating IQ, language function, and visual motor integration. Multiple hierarchical regressions examined associations of DGM growth with neuropsychological measures. Overall DGM growth, primarily attributed to the caudate and thalamus, predicted Full Scale IQ, core language and VMI scores after controlling for sex and total brain volume. Thalamic growth was additionally associated with measures of neonatal clinical severity, bronchopulmonary dysplasia, and white matter lesions. Longitudinal growth of the DGM, particularly the caudate and thalamus were established as early markers of long-term outcomes.

Definition of neurodevelopmental outcome from early brain imaging remains a priority for survivors of very preterm (VPT) birth given their persistently high rates of cognitive and motor difficulties. Volumes of the deep grey matter (DGM) structures were measured longitudinally using magnetic resonance imaging from 96 VPT infants studied within 2 weeks of birth and 70 at term-equivalent age. At 4 years of age, 36 children returned for neuropsychological assessments evaluating IQ, language function, and visual motor integration. Multiple hierarchical regressions examined associations of DGM growth with neuropsychological measures. Overall DGM growth, primarily attributed to the caudate and thalamus, predicted Full Scale IQ, core language and VMI scores after controlling for sex and total brain volume. Thalamic growth was additionally associated with measures of neonatal clinical severity, bronchopulmonary dysplasia, and white matter lesions. Longitudinal growth of the DGM, particularly the caudate and thalamus were established as early markers of long-term outcomes.

The presence of white matter hyperintensities (WMH) and silent infarcts on magnetic resonance imaging is a common finding in elderly individuals. This subcortical ischemic vasculopathy is associated with age and cerebrovascular risk factors and can increase the risk of dementia, yet the contribution of subcortical vascular disease to the clinical profile and progression of Alzheimer’s disease patients is still relatively poorly understood. This study assessed the presence, severity and progression of WMH and lacunar infarcts and studied their relationship with measures of brain function and cognition in 64 patients with Alzheimer’s disease. Both a visual rating scale and volumetric tissue segmentation analysis were used to evaluate brain-behaviour relationships of WMH seen on T2-weighted and Proton Density MRI scans. In addition to describing the topographical distribution of WMH and lacunes, and examining sex differences, the volume and location of WMH were correlated with executive function, frontal lobe perfusion, and medial temporal lobe atrophy. The results confirm and extend previous findings suggesting that WMH are located primarily in the frontal and parietal regions and are associated with mild decline in tasks of executive function. WMH severity was not associated with a decrease in frontal lobe perfusion as measured by Single Photon Emission Computed Tomography. The investigation of different WMH subtypes revealed that lacunar infarcts were found most often within deep WMH. At one year follow-up, progression was seen in deep WMH, specifically in the frontal lobe and in lacunes found within the periventricular regions. Furthermore, progression in WMH was associated with a decline in cognition. Taken together, these studies indicate the utility of measuring WMH by subtype (periventricular and deep WMH and lacunes) in understanding progression patterns and brain-behavior relationships. Since, subcortical ischemic vasculopathy may be potentially preventable; this study underlines the need to study interventions that address risk factors for the development of small vessel cerebrovascular disease, which may be helpful in preventing disability in the elderly.

The study of brain temperature is important for a number of clinical conditions such as stroke, traumatic brain injury, schizophrenia and birth asphyxia (for neonates). A direct method to estimate brain temperature non-invasively will allow assessment of brain thermoregulation and its variation in clinical conditions. Magnetic resonance imaging is a powerful technique widely used for diagnosis of a range of neurological conditions. All magnetic resonance procedures involve manipulation of the hydrogen nuclei in the water molecules of the human body. The resonance frequency of the water molecules is temperature dependent, thus MR thermometry is a powerful tool for non-invasive temperature measurement. Using internal reference MR spectroscopic imaging (MRSI), absolute brain temperature maps can be estimated. However a number of temperature independent factors influence MRSI data acquisition, thus a thorough validation is necessary and is the focus of this PhD study. In this PhD study using phantom (test object) studies it was shown that optimization of the MRSI pulse sequence is necessary to reduce systematic error in temperature maps and extensive in-vitro validation of MRSI temperature mapping was performed. A custom made temperature-controlled phantom was designed for this purpose and is presented in this thesis. MRSI data acquired from healthy (young and elderly) volunteers was employed to assess regional brain temperature variations and repeatability. Finally, the feasibility of employing fast echo planar spectroscopic imaging for volumetric MRSI temperature mapping will be presented in this thesis.